Selective titanium nitride etching

ABSTRACT

Methods of etching exposed titanium nitride with respect to other materials on patterned heterogeneous structures are described, and may include a remote plasma etch formed from a fluorine-containing precursor. Precursor combinations including plasma effluents from the remote plasma are flowed into a substrate processing region to etch the patterned structures with high titanium nitride selectivity under a variety of operating conditions. The methods may be used to remove titanium nitride at faster rates than a variety of metal, nitride, and oxide compounds.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/740,587, filed Dec. 21, 2012, entitled “Selective Titanium NitrideEtching.” The entire disclosure of which is incorporated herein byreference for all purposes.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment.More specifically, the present technology relates to selective etchingof materials on semiconductor substrates.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

A wet HF etch preferentially removes silicon oxide over otherdielectrics and semiconductors. However, wet processes are unable topenetrate some constrained trenches and sometimes deform the remainingmaterial. Dry etches produced in local plasmas formed within thesubstrate processing region can penetrate more constrained trenches andexhibit less deformation of delicate remaining structures. However,local plasmas can damage the substrate through the production ofelectric arcs as they discharge.

Thus, there is a need for improved methods and systems for selectivelyetching materials and structures on semiconductor substrates. These andother needs are addressed by the present technology.

SUMMARY

Methods of etching exposed titanium nitride with respect to othermaterials on patterned heterogeneous structures are described, and mayinclude a remote plasma etch formed from a fluorine-containingprecursor. Precursor combinations including plasma effluents from theremote plasma are flowed into a substrate processing region to etch thepatterned structures with high titanium nitride selectivity under avariety of operating conditions. The methods may be used to removetitanium nitride at faster rates than a variety of metal, nitride, andoxide compounds.

The at least one additional precursor may include one or more precursorsselected from the group consisting of helium, argon, and molecularhydrogen (H₂). The fluorine-containing precursor may include one or moreprecursors selected from the group consisting of atomic fluorine,diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride, hydrogenfluoride, and xenon difluoride. The methods may be performed such thatthe processing region in which the semiconductor substrate resides isplasma-free during the etching process.

The methods may include having the additional precursor consist of oneor both of helium and argon. The precursor combination delivered intothe processing region may be substantially devoid of hydrogen. Theexposed second material may include silicon oxide and/or siliconnitride, and the selectivity of the etching operation (exposed titaniumnitride region: exposed silicon oxide region) may be greater than orabout 5:1, and in disclosed embodiments may be greater than or about10:1. The substrate temperature may be maintained below or about 50° C.during the etch process, and in disclosed embodiments may be maintainedat or below about 10° C. during the etch process.

The methods can include that the at least one additional precursorcomprises hydrogen, and may additionally include one or more carriergases including helium or argon. The exposed second material may includetungsten, and the selectivity of the etching operation (exposed titaniumnitride region: exposed tungsten region) may be greater than or about50:1, and in disclosed embodiments may be greater than or about 100:1.The patterned substrate may further include additional exposed regionsor materials, and in disclosed embodiments the substrate furthercomprises an exposed silicon nitride region. The selectivity of theetching operation (exposed titanium nitride region: exposed siliconnitride region) may be greater than or about 10:1. The patternedsubstrate may further include an exposed silicon oxide region, and theselectivity of the etching operation (exposed titanium nitride region:exposed silicon oxide region) may be greater than or about 5:1. Thepatterned substrate may further include an exposed tantalum nitrideregion, and the selectivity of the etching operation (exposed titaniumnitride region: exposed tantalum nitride region) may be greater than orabout 10:1. The substrate temperature may be maintained at or aboveabout 50° C. during the etch process, and in disclosed embodiments maybe maintained at or above about 200° C. during the etch process. Themethod may include flowing the hydrogen into the substrate processingregion without its being excited by any remote plasma prior to enteringthe processing region. The plasma utilized in the methods in the remoteplasma region may be a capacitively-coupled plasma.

Such technology may provide numerous benefits over conventionaltechniques. For example, process throughput may be increased based onthe improved selectivity. Additionally, less protection of exposedmaterials may be required with the improved selective etching withrespect to multiple materials. These and other embodiments, along withmany of their advantages and features, are described in more detail inconjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedtechnology may be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a flow chart of a titanium nitride selective etch processaccording to disclosed embodiments.

FIG. 2A shows a schematic cross-sectional view of a substrate processingchamber according to the disclosed technology.

FIG. 2B shows a schematic cross-sectional view of a portion of asubstrate processing chamber according to the disclosed technology.

FIG. 2C shows a bottom plan view of a showerhead according to thedisclosed technology.

FIG. 3 shows a top plan view of an exemplary substrate processing systemaccording to the disclosed technology.

In the appended figures, similar components and/or features may have thesame numerical reference label. Further, various components of the sametype may be distinguished by following the reference label by a letterthat distinguishes among the similar components and/or features. If onlythe first numerical reference label is used in the specification, thedescription is applicable to any one of the similar components and/orfeatures having the same first numerical reference label irrespective ofthe letter suffix.

DETAILED DESCRIPTION

The present technology includes improved processes and chemistryprofiles for removing titanium nitride on patterned semiconductorsubstrates with respect to other materials. While conventional processesmay remove titanium nitride at slower or equal rates than othermaterials, the presently described technology allows for improved ratesof titanium nitride removal. In so doing, substrate throughput may beimproved in a variety of ways. For example, the rate at whichcompositions are etched may be increased. Additionally, less materialmay be required as initially deposited or located in, on, or as part ofthe patterned substrate with respect to the titanium nitride to beremoved. If additional material located on the substrate with titaniumnitride is to be maintained, but etches at the same rate as titaniumnitride, for example, additional material would generally need to beinitially deposited or located beyond what is to be maintained that isproportional to the etch rate with respect to the amount of titaniumnitride to be removed. Accordingly, process times may increase. However,if the selectivity to titanium nitride can be increased, less of thesecond material will be removed, and less additional material would needto have been initially deposited or located on the substrate.Accordingly, process times can be reduced.

Methods of etching exposed titanium nitride with respect to othermaterials on patterned heterogeneous structures are described, and mayinclude a remote plasma etch formed from a fluorine-containingprecursor. Precursor combinations including plasma effluents from theremote plasma are flowed into a substrate processing region to etch thepatterned structures with high titanium nitride selectivity under avariety of operating conditions. The methods may be used to removetitanium nitride at faster rates than a variety of metal, nitride, andoxide compounds.

Selective dry etch processes may be used to remove one material withrespect to another material on patterned semiconductor substrates.However, depending on the exposed materials, process gases and processconditions may not provide adequate etch rates of one material withoutdamaging exposed features of another material. The presence of certainprecursor chemicals may directly affect the etch rates and selectivitiesof a variety of materials. The inventors have advantageously determinedthat the selectivity of titanium nitride over a variety of materials canbe enhanced by exciting a fluorine-containing precursor in a remoteplasma, and limiting the additional precursors that are used inconjunction with the fluorine-containing precursor based on the materialthat is to be maintained.

In order to better understand and appreciate the invention, reference isnow made to FIG. 1, which shows a flow chart of a titanium nitrideselective etch process according to disclosed embodiments. Prior to thefirst operation, the substrate may be patterned leaving exposed regionsof titanium nitride and exposed regions of a second material that mayinclude one or more of tantalum nitride, tungsten, silicon nitride,silicon oxide, etc. Various front end processing may have been performedincluding the formation of gates, vias, and other structures. Thepatterned substrate may then be delivered to a substrate processingregion at operation 110. In disclosed embodiments, the substrate mayalready be located in the processing region if a previous operation wasperformed in the same chamber in which the etch process is to occur.Nitrogen trifluoride (NF₃) may be flowed into a plasma region that isseparate from, but fluidly coupled with, the processing region atoperation 120. Other sources of fluorine may be used in conjunction withor as replacements for the nitrogen trifluoride. In general, afluorine-containing precursor is flowed into the plasma region and thefluorine-containing precursor comprises at least one precursor selectedfrom the group consisting of atomic fluorine, diatomic fluorine,nitrogen trifluoride, carbon tetrafluoride, hydrogen fluoride, and xenondifluoride.

The separate plasma region may be referred to as a remote plasma regionherein and may be within a distinct module from the processing chamber,or as a compartment within the processing chamber. A plasma may beformed within the remote plasma region thereby generating plasmaeffluents from the fluorine-containing precursor. At operation 130, oneor more additional precursors may be flowed that are either additionallyflowed into the plasma region, or directed to bypass the plasma regionto flow unexcited into the processing region. The additional precursorsmay include carrier gases, such as for example helium or argon, and mayadditionally include a hydrogen source, including molecular hydrogen(H₂) in disclosed embodiments. The combination of precursors includingthe plasma effluents is directed to flow into the processing region atoperation 140. As previously stated, the precursors may have beenpre-mixed in the remote plasma region, or the precursors may be fluidlyisolated from one another until they are separately delivered into theprocessing region.

The patterned substrate may be selectively etched with the precursorcombination including plasma effluents at operation 150, such that theexposed titanium nitride region is removed at a higher rate than theexposed second material on the patterned substrate. The reactivechemical species may be removed from the substrate processing region,and then the substrate may be removed from the processing region atoperation 160. Using the gas phase dry etch processes described herein,the inventors have established that etch selectivities of over 5:1 withregard to the titanium nitride etch rate as compared to the etch rate ofother materials are possible. Achievable selectivities using the methodsdescribed herein are additionally capable of etching titanium nitride atrates faster than a second material that typically etches faster thantitanium nitride, such as tungsten, as will be described in greaterdetail below. The titanium nitride etch rate may exceed the exposedsecond material etch rate by a multiplicative factor of up to or about 5or more, about 10 or more, about 15 or more, about 20 or more, about 50or more, about 75 or more, about 100 or more, etc. or greater inembodiments of the technology.

Depending on the additional precursor or precursors used in theexemplary processes, the rates of titanium nitride etching with respectto the exposed second material may by affected. For example, indisclosed embodiments the additional precursor may be one or moreprecursors selected from the group consisting of helium, argon, andmolecular hydrogen (H₂). In other embodiments, other hydrogen-containingprecursors may be used including ammonia, for example. Depending on whatadditional materials are exposed, these gases may be used in combinationto adjust etch characteristics.

When the exposed materials include titanium nitride and certain othermaterials including silicon nitride or silicon oxide, the one or moreadditional precursors may include only carrier gases, such as heliumand/or argon. In one embodiment, the additional precursors consistexclusively of helium and/or argon. Put another way, the precursorcombination including plasma effluents delivered to the processingregion may be completely or substantially devoid of any hydrogen orhydrogen-containing precursors. The additional precursors may be flowedwith the fluorine-containing precursor into the plasma region to produceplasma effluents. When these precursor combinations including plasmaeffluents are delivered into the processing region, the selectivity ofthe etching operation of an exposed titanium nitride region to anexposed silicon oxide region may be up to, greater than, or about 2:1.The etching selectivity may also be up to, greater than, or about 5:1,10:1, 15:1, 17:1, 20:1, etc. or more. In terms of material etched, inone minute of processing time about 100 Angstrom or more of titaniumnitride may be etched while less than or about 20 Angstrom of siliconoxide may be removed. In other embodiments less than or about 15Angstrom, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or 0 Angstrom of siliconoxide may be removed, the last case indicating that the silicon oxide ismaintained during the etching of titanium nitride.

During the etching process, the substrate may be maintained at or belowabout 400° C., and may be maintained at or below about 300° C., 200° C.,100° C., 80° C., 75° C., 50° C., 25° C., 10° C., 0° C., or less. Theprocessing chamber may be maintained at or below about 100 Torr duringthe processes, and may be maintained at or below about 50 Torr, 25 Torr,15 Torr, 5 Torr, 1 Torr, 0.1 Torr, etc., or between about 0.1 mTorr andabout 10 Torr. By maintaining the substrate temperature at lowertemperatures, such as about 10° C. or less, and maintaining the processchamber at a pressure below about 10 Torr, the inventors have determinedthat the amount of oxide removal can be further limited during theremoval of titanium nitride.

Certain materials may typically etch at a faster rate than titaniumnitride, including other metals such as tungsten. For example, if theabove-described etch process is performed, any exposed tungsten may etchfaster than the exposed titanium nitride. If a region of titaniumnitride is to be removed, but an exposed region of tungsten is to bemaintained, these etching processes may be difficult to control and maydamage the tungsten features. To address the selectivity of tungsten totitanium nitride, the inventors have determined that by includinghydrogen as one of the additional precursors, the rate at which tungstenetches may be slowed significantly such that the selectivity to titaniumnitride reverses, and in disclosed embodiments the rate at whichtungsten is etched can be reduced to about zero.

In embodiments, the precursors may include molecular hydrogen with thefluorine-containing radical, or alternatively a hydrogen-containingprecursor. The hydrogen may be included with the fluorine-containingradical and carrier gas or gases discussed above that are delivered intothe remote plasma region where the plasma effluents are developed.Alternatively, the hydrogen may be delivered separately from thefluorine-containing precursor such that it bypasses the remote plasmaregion. For example, when a dual-channel showerhead such as thatdiscussed below is utilized, the hydrogen may be delivered into thevolume defined by the showerhead plates. Accordingly, the hydrogen maybe delivered to the processing region without being excited by anyremote plasma, and it may not come into contact with the plasmaeffluents until it enters the processing region.

When these precursor combinations including hydrogen and containingplasma effluents are delivered into the processing region, theselectivity of the etching operation of an exposed titanium nitrideregion to an exposed tungsten region may be up to, greater than, orabout 10:1. The etching selectivity may also be up to, greater than, orabout 20:1, 50:1, 100:1, 500:1, 1000:1, etc. or more, up to the point atwhich the process is fully selective to titanium nitride and no tungstenis removed. In terms of material etched, in one minute of processingtime up to or about 3 Angstrom or more, 6 Angstrom or more, or 10Angstrom or more of titanium nitride may be etched while less than orabout 1 Angstrom of tungsten may be removed. In other embodiments lessthan or about 0.5 Angstrom, 0.1, 0.05, 0.01, 0.005, 0.001, 0.0001, or 0Angstrom of tungsten may be removed, that last case of which indicatesthat the exposed tungsten region is completely maintained.

This process may additionally remove titanium nitride with respect toother materials as well. For example, when titanium nitride is used ingate applications as an interface layer, or as a hard mask forpatterning low-k stacks, additionally exposed materials may include oneor more materials such as metals including tungsten, and materialsincluding silicon nitride, silicon oxide, and tantalum nitride. In manyapplications, these layers are to be maintained as much as possibleduring the titanium nitride removal. Utilizing the processes encompassedby this technology, titanium nitride may be etched with respect to allof these materials, and the selectivity to titanium nitride with respectto each material may be at least or about 5:1. In disclosed embodiments,titanium nitride may be etched with respect to silicon oxide, and theselectivity of the etching operation may be greater than or about 2:1,or greater than or about 5:1. Titanium nitride may be etched withrespect to silicon nitride, and the selectivity of the etching operationmay be greater than or about 5:1, or greater than or about 10:1.Titanium nitride may also be etched with respect to tantalum nitride,and the selectivity of the etching operation may be greater than orabout 5:1, or greater than or about 10:1.

By utilizing the hydrogen precursor, the plasma density with respect tothe fluorine-containing precursor may be reduced, which may reduce theetch rate of the materials. This in turn may reduce the substratethroughput for these processes. Etch rate may often be increased byincreasing the substrate temperature, but this may also increase therate at which materials to be maintained are etched. However, theinventors have determined that the process chemistries utilizinghydrogen described in this technology may act synergistically when thetemperatures are raised, such that the rate at which titanium nitride isremoved may increase faster than the etch rate of other materials to bemaintained. Accordingly, the processes may allow the substrate to bemaintained at or above about 0° C. or between about 0° C. and about 400°C., but may also be maintained at or above about 10° C., 25° C., 50° C.,75° C., 80° C., 100° C., 200° C., 300° C., 400° C., or more. Theprocessing chamber may be maintained at or below about 100 Torr, and maybe maintained at or below about 50 Torr, 25 Torr, 15 Torr, 5 Torr, 1Torr, 0.1 Torr, etc., or between about 0.1 mTorr and about 10 Torr.

The described processes may also be used in conjunction with one anotherfor a variety of operations in which tungsten and titanium nitride maybe both located and exposed on patterned substrates. For example, ingate structures including NAND or 3D NAND devices, both tungsten andtitanium nitride may be located on the substrate as gate metal andbarrier material respectively. During processing, the exposed gate metalmay need to be recessed while maintaining a portion of titanium nitride,or otherwise etching the titanium nitride at a slower rate. Accordingly,the described chemistry devoid of hydrogen may be utilized at a lowersubstrate temperature, which may remove tungsten at a rate faster thantitanium nitride.

The recessing operation may expose regions or additional regions oftitanium nitride, and may additionally expose regions of tantalumnitride, silicon nitride, and silicon oxide, for example. Once thetungsten has been recessed but otherwise maintained, further etching ofthe titanium nitride and or other exposed materials may be neededwithout further etching, or with minimal further etching, of theremaining tungsten. Accordingly, the described process synergisticallyutilizing hydrogen as a precursor with increased temperature may beperformed. For example, the substrate temperature may be increased whilehydrogen is incorporated with the precursor fluids. Consequently,further etching of the tungsten may be minimized while exposed titaniumnitride may be removed. In this way, by combining these etchingprocesses, etching of titanium nitride with respect to tungsten may bemodified tuned in situ. By utilizing the combined processes, tungstenmay be etched faster than titanium nitride, titanium nitride may beetched faster than tungsten, or the two materials may be etched atsubstantially similar or directly equivalent rates by adjusting thehydrogen concentration and/or certain of the processing conditions suchas temperature. As would be understood, additional modifications tochamber pressure and plasma power may be used to further tune theetching processes as may be required. Advantageously, tuning theseprocesses may be performed without the need to break vacuum conditionsor move the substrate to an additional chamber. This may reduce overallprocessing times and save costs over conventional techniques. Additionalexamples of etch process parameters, chemistries, and components aredisclosed in the course of describing an exemplary processing chamberand system below.

Exemplary Processing System

FIG. 2A shows a cross-sectional view of an exemplary process chambersection 200 with partitioned plasma generation regions within theprocessing chamber. During film etching, e.g., titanium nitride,tantalum nitride, tungsten, silicon, polysilicon, silicon oxide, siliconnitride, silicon oxynitride, silicon oxycarbide, etc., a process gas maybe flowed into the first plasma region 215 through a gas inlet assembly205. A remote plasma system (RPS) 201 may optionally be included in thesystem, and may process a first gas which then travels through gas inletassembly 205. The inlet assembly 205 may include two or more distinctgas supply channels where the second channel (not shown) may bypass theRPS 201, if included. Accordingly, in disclosed embodiments theprecursor gases may be delivered to the processing chamber in anunexcited state. In another example, the first channel provided throughthe RPS may be used for the process gas and the second channel bypassingthe RPS may be used for a treatment gas in disclosed embodiments. Theprocess gas may be excited within the RPS 201 prior to entering thefirst plasma region 215. Accordingly, the fluorine-containing precursoras discussed above, for example, may pass through RPS 201 or bypass theRPS unit in disclosed embodiments. Various other examples encompassed bythis arrangement will be similarly understood.

A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225,and a substrate support 265, having a substrate 255 disposed thereon,are shown and may each be included according to disclosed embodiments.The pedestal 265 may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate. Thisconfiguration may allow the substrate 255 temperature to be cooled orheated to maintain relatively low temperatures, such as between about−20° C. to about 200° C., or therebetween. The heat exchange fluid maycomprise ethylene glycol and/or water. The wafer support platter of thepedestal 265, which may comprise aluminum, ceramic, or a combinationthereof, may also be resistively heated in order to achieve relativelyhigh temperatures, such as from up to or about 100° C. to above or about1100° C., using an embedded resistive heater element. The heatingelement may be formed within the pedestal as one or more loops, and anouter portion of the heater element may run adjacent to a perimeter ofthe support platter, while an inner portion runs on the path of aconcentric circle having a smaller radius. The wiring to the heaterelement may pass through the stem of the pedestal 265, which may befurther configured to rotate.

The faceplate 217 may be pyramidal, conical, or of another similarstructure with a narrow top portion expanding to a wide bottom portion.The faceplate 217 may additionally be flat as shown and include aplurality of through-channels used to distribute process gases. Plasmagenerating gases and/or plasma excited species, depending on use of theRPS 201, may pass through a plurality of holes, shown in FIG. 2B, infaceplate 217 for a more uniform delivery into the first plasma region215.

Exemplary configurations may include having the gas inlet assembly 205open into a gas supply region 258 partitioned from the first plasmaregion 215 by faceplate 217 so that the gases/species flow through theholes in the faceplate 217 into the first plasma region 215. Structuraland operational features may be selected to prevent significant backflowof plasma from the first plasma region 215 back into the supply region258, gas inlet assembly 205, and fluid supply system 210. The structuralfeatures may include the selection of dimensions and cross-sectionalgeometries of the apertures in faceplate 217 to deactivateback-streaming plasma. The operational features may include maintaininga pressure difference between the gas supply region 258 and first plasmaregion 215 that maintains a unidirectional flow of plasma through theshowerhead 225. The faceplate 217, or a conductive top portion of thechamber, and showerhead 225 are shown with an insulating ring 220located between the features, which allows an AC potential to be appliedto the faceplate 217 relative to showerhead 225 and/or ion suppressor223. The insulating ring 220 may be positioned between the faceplate 217and the showerhead 225 and/or ion suppressor 223 enabling a capacitivelycoupled plasma (CCP) to be formed in the first plasma region. A baffle(not shown) may additionally be located in the first plasma region 215,or otherwise coupled with gas inlet assembly 205, to affect the flow offluid into the region through gas inlet assembly 205.

The ion suppressor 223 may comprise a plate or other geometry thatdefines a plurality of apertures throughout the structure that areconfigured to suppress the migration of ionically-charged species out ofthe plasma excitation region 215 while allowing uncharged neutral orradical species to pass through the ion suppressor 223 into an activatedgas delivery region between the suppressor and the showerhead. Indisclosed embodiments, the ion suppressor 223 may comprise a perforatedplate with a variety of aperture configurations. These uncharged speciesmay include highly reactive species that are transported with lessreactive carrier gas through the apertures. As noted above, themigration of ionic species through the holes may be reduced, and in someinstances completely suppressed. Controlling the amount of ionic speciespassing through the ion suppressor 223 may provide increased controlover the gas mixture brought into contact with the underlying wafersubstrate, which in turn may increase control of the deposition and/oretch characteristics of the gas mixture. For example, adjustments in theion concentration of the gas mixture can significantly alter its etchselectivity, e.g., TiNx:SiOx etch ratios, TiN:W etch ratios, etc. Inalternative embodiments in which deposition is performed, it can alsoshift the balance of conformal-to-flowable style depositions fordielectric materials.

The plurality of holes in the ion suppressor 223 may be configured tocontrol the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 223. For example, theaspect ratio of the holes, or the hole diameter to length, and/or thegeometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 223 is reduced. The holes in the ion suppressor 223 mayinclude a tapered portion that faces the plasma excitation region 215,and a cylindrical portion that faces the showerhead 225. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 225. An adjustable electrical bias mayalso be applied to the ion suppressor 223 as an additional means tocontrol the flow of ionic species through the suppressor.

The ion suppression element 223 may function to reduce or eliminate theamount of ionically charged species traveling from the plasma generationregion to the substrate. Uncharged neutral and radical species may stillpass through the openings in the ion suppressor to react with thesubstrate. It should be noted that the complete elimination of ionicallycharged species in the reaction region surrounding the substrate is notalways the desired goal. In many instances, ionic species are requiredto reach the substrate in order to perform the etch and/or depositionprocess. In these instances, the ion suppressor may help to control theconcentration of ionic species in the reaction region at a level thatassists the process.

Showerhead 225 in combination with ion suppressor 223 may allow a plasmapresent in chamber plasma region 215 to avoid directly exciting gases insubstrate processing region 233, while still allowing excited species totravel from chamber plasma region 215 into substrate processing region233. In this way, the chamber may be configured to prevent the plasmafrom contacting a substrate 255 being etched. This may advantageouslyprotect a variety of intricate structures and films patterned on thesubstrate, which may be damaged, dislocated, or otherwise warped ifdirectly contacted by a generated plasma. Additionally, when plasma isallowed to contact the substrate or approach the substrate level, therate at which oxide species etch may increase. Accordingly, if theexposed second material is oxide, this material may be further protectedby maintaining the plasma remotely from the substrate.

The processing system may further include a power supply 240electrically coupled with the processing chamber to provide electricpower to the faceplate 217, ion suppressor 223, showerhead 225, and/orpedestal 265 to generate a plasma in the first plasma region 215 orprocessing region 233. The power supply may be configured to deliver anadjustable amount of power to the chamber depending on the processperformed. Such a configuration may allow for a tunable plasma to beused in the processes being performed. Unlike a remote plasma unit,which is often presented with on or off functionality, a tunable plasmamay be configured to deliver a specific amount of power to the plasmaregion 215. This in turn may allow development of particular plasmacharacteristics such that precursors may be dissociated in specific waysto enhance the etching profiles produced by these precursors.

A plasma may be ignited either in chamber plasma region 215 aboveshowerhead 225 or substrate processing region 233 below showerhead 225.A plasma may be present in chamber plasma region 215 to produce theradical-fluorine precursors from an inflow of the fluorine-containingprecursor. An AC voltage typically in the radio frequency (RF) range maybe applied between the conductive top portion of the processing chamber,such as faceplate 217, and showerhead 225 and/or ion suppressor 223 toignite a plasma in chamber plasma region 215 during deposition. An RFpower supply may generate a high RF frequency of 13.56 MHz but may alsogenerate other frequencies alone or in combination with the 13.56 MHzfrequency.

Plasma power can be of a variety of frequencies or a combination ofmultiple frequencies. In the exemplary processing system the plasma maybe provided by RF power delivered to faceplate 217 relative to ionsuppressor 223 and/or showerhead 225. The RF power may be between about10 watts and about 2000 watts, between about 100 watts and about 2000watts, between about 200 watts and about 1500 watts, or between about200 watts and about 1000 watts in different embodiments. The RFfrequency applied in the exemplary processing system may be low RFfrequencies less than about 200 kHz, high RF frequencies between about10 MHz and about 15 MHz, or microwave frequencies greater than or about1 GHz in different embodiments. The plasma power may becapacitively-coupled (CCP) or inductively-coupled (ICP) into the remoteplasma region.

The top plasma region 215 may be left at low or no power when a bottomplasma in the substrate processing region 233 is turned on to, forexample, cure a film or clean the interior surfaces bordering substrateprocessing region 233. A plasma in substrate processing region 233 maybe ignited by applying an AC voltage between showerhead 255 and thepedestal 265 or bottom of the chamber. A cleaning gas may be introducedinto substrate processing region 233 while the plasma is present.

A fluid, such as a precursor, for example a fluorine-containingprecursor, may be flowed into the processing region 233 by embodimentsof the showerhead described herein. Excited species derived from theprocess gas in the plasma region 215 may travel through apertures in theion suppressor 223, and/or showerhead 225 and react with an additionalprecursor flowing into the processing region 233 from a separate portionof the showerhead. Alternatively, if all precursor species are beingexcited in plasma region 215, no additional precursors may be flowedthrough the separate portion of the showerhead. Little or no plasma maybe present in the processing region 233. Excited derivatives of theprecursors may combine in the region above the substrate and, onoccasion, on the substrate to etch structures or remove species on thesubstrate in disclosed applications.

Exciting the fluids in the first plasma region 215 directly, or excitingthe fluids in the RPS units 201, may provide several benefits. Theconcentration of the excited species derived from the fluids may beincreased within the processing region 233 due to the plasma in thefirst plasma region 215. This increase may result from the location ofthe plasma in the first plasma region 215. The processing region 233 maybe located closer to the first plasma region 215 than the remote plasmasystem (RPS) 201, leaving less time for the excited species to leaveexcited states through collisions with other gas molecules, walls of thechamber, and surfaces of the showerhead.

The uniformity of the concentration of the excited species derived fromthe process gas may also be increased within the processing region 233.This may result from the shape of the first plasma region 215, which maybe more similar to the shape of the processing region 233. Excitedspecies created in the RPS 201 may travel greater distances in order topass through apertures near the edges of the showerhead 225 relative tospecies that pass through apertures near the center of the showerhead225. The greater distance may result in a reduced excitation of theexcited species and, for example, may result in a slower growth ratenear the edge of a substrate. Exciting the fluids in the first plasmaregion 215 may mitigate this variation for the fluid flowed through RPS201, or alternatively bypassed around the RPS unit.

The processing gases may be excited in first plasma region 215 and maybe passed through the showerhead 225 to the processing region 233 in theexcited state. While a plasma may be generated in the processing region233, a plasma may alternatively not be generated in the processingregion. In one example, the only excitation of the processing gas orprecursors may be from exciting the processing gases in plasma region215 to react with one another in the processing region 233. Aspreviously discussed, this may be to protect the structures patterned onthe substrate 255.

In addition to the fluid precursors, there may be other gases introducedat varied times for varied purposes, including carrier gases to aiddelivery. A treatment gas may be introduced to remove unwanted speciesfrom the chamber walls, the substrate, the deposited film and/or thefilm during deposition. A treatment gas may be excited in a plasma andthen used to reduce or remove residual content inside the chamber. Inother disclosed embodiments the treatment gas may be used without aplasma. When the treatment gas includes water vapor, the delivery may beachieved using a mass flow meter (MFM), an injection valve, or bycommercially available water vapor generators. The treatment gas may beintroduced to the processing region 233, either through the RPS unit orbypassing the RPS unit, and may further be excited in the first plasmaregion.

FIG. 2B shows a detailed view of the features affecting the processinggas distribution through faceplate 217. As shown in FIGS. 2A and 2B,faceplate 217, cooling plate 203, and gas inlet assembly 205 intersectto define a gas supply region 258 into which process gases may bedelivered from gas inlet 205. The gases may fill the gas supply region258 and flow to first plasma region 215 through apertures 259 infaceplate 217. The apertures 259 may be configured to direct flow in asubstantially unidirectional manner such that process gases may flowinto processing region 233, but may be partially or fully prevented frombackflow into the gas supply region 258 after traversing the faceplate217.

The gas distribution assemblies such as showerhead 225 for use in theprocessing chamber section 200 may be referred to as dual channelshowerheads (DCSH) and are additionally detailed in the embodimentsdescribed in FIG. 2A as well as FIG. 2C herein. The dual channelshowerhead may provide for etching processes that allow for separationof etchants outside of the processing region 233 to provide limitedinteraction with chamber components and each other prior to beingdelivered into the processing region.

The showerhead 225 may comprise an upper plate 214 and a lower plate216. The plates may be coupled with one another to define a volume 218between the plates. The coupling of the plates may be so as to providefirst fluid channels 219 through the upper and lower plates, and secondfluid channels 221 through the lower plate 216. The formed channels maybe configured to provide fluid access from the volume 218 through thelower plate 216 via second fluid channels 221 alone, and the first fluidchannels 219 may be fluidly isolated from the volume 218 between theplates and the second fluid channels 221. The volume 218 may be fluidlyaccessible through a side of the gas distribution assembly 225. Althoughthe exemplary system of FIG. 2 includes a dual-channel showerhead, it isunderstood that alternative distribution assemblies may be utilized thatmaintain first and second precursors fluidly isolated prior to theprocessing region 233. For example, a perforated plate and tubesunderneath the plate may be utilized, although other configurations mayoperate with reduced efficiency or not provide as uniform processing asthe dual-channel showerhead as described.

In the embodiment shown, showerhead 225 may distribute via first fluidchannels 219 process gases which contain plasma effluents uponexcitation by a plasma in chamber plasma region 215. In embodiments, theprocess gas introduced into the RPS 201 and/or chamber plasma region 215may contain fluorine, e.g., CF₄, NF₃ or XeF₂. The process gas may alsoinclude a carrier gas such as helium, argon, nitrogen (N₂), etc. Plasmaeffluents may include ionized or neutral derivatives of the process gasand may also be referred to herein as a radical-fluorine precursorreferring to the atomic constituent of the process gas introduced.

FIG. 2C is a bottom view of a showerhead 225 for use with a processingchamber according to disclosed embodiments. Showerhead 225 correspondswith the showerhead shown in FIG. 2A. Through-holes 231, which show aview of first fluid channels 219, may have a plurality of shapes andconfigurations in order to control and affect the flow of precursorsthrough the showerhead 225. Small holes 227, which show a view of secondfluid channels 221, may be distributed substantially evenly over thesurface of the showerhead, even amongst the through-holes 231, which mayhelp to provide more even mixing of the precursors as they exit theshowerhead than other configurations.

An additional dual channel showerhead, as well as this processing systemand chamber, are more fully described in patent application Ser. No.13/251,714 filed on Oct. 3, 2011, which is hereby incorporated byreference for all purposes to the extent not inconsistent with theclaimed features and description herein.

The chamber plasma region 215 or a region in an RPS may be referred toas a remote plasma region. In embodiments, the radical precursor, e.g.,a radical-fluorine precursor, is created in the remote plasma region andtravels into the substrate processing region where it may or may notcombine with additional precursors. In embodiments, the additionalprecursors are excited only by the radical-fluorine precursor. Plasmapower may essentially be applied only to the remote plasma region inembodiments to ensure that the radical-fluorine precursor provides thedominant excitation. Nitrogen trifluoride or another fluorine-containingprecursor may be flowed into chamber plasma region 215 at rates betweenabout 25 sccm and about 500 sccm, between about 50 sccm and about 150sccm, or between about 75 sccm and about 125 sccm in differentembodiments.

Combined flow rates of precursors into the chamber may account for 0.05%to about 20% by volume of the overall gas mixture; the remainder beingcarrier gases. The fluorine-containing precursor may be flowed into theremote plasma region, but the plasma effluents may have the samevolumetric flow ratio in embodiments. In the case of thefluorine-containing precursor, a purge or carrier gas may be firstinitiated into the remote plasma region before the fluorine-containinggas to stabilize the pressure within the remote plasma region.

Substrate processing region 233 can be maintained at a variety ofpressures during the flow of precursors, any carrier gases, and plasmaeffluents into substrate processing region 233. The pressure may bemaintained between about 0.1 mTorr and about 100 Torr, between about 1Torr and about 20 Torr or between about 1 Torr and about 5 Torr indifferent embodiments.

Embodiments of the deposition systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 3 showsone such system 300 of deposition, etching, baking, and curing chambersaccording to disclosed embodiments. In the figure, a pair of frontopening unified pods (FOUPs) 302 supply substrates of a variety of sizesthat are received by robotic arms 304 and placed into a low pressureholding area 306 before being placed into one of the substrateprocessing chambers 308 a-f. A second robotic arm 310 may be used totransport the substrate wafers from the holding area 306 to thesubstrate processing chambers 308 a-f and back. Each substrateprocessing chamber 308 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes.

The substrate processing chambers 308 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a dielectricfilm on the substrate wafer. In one configuration, two pairs of theprocessing chamber, e.g., 308 c-d and 308 e-f, may be used to depositdielectric material on the substrate, and the third pair of processingchambers, e.g., 308 a-b, may be used to etch the deposited dielectric.In another configuration, all three pairs of chambers, e.g., 308 a-f,may be configured to etch a dielectric film on the substrate. Any one ormore of the processes described may be carried out in chamber(s)separated from the fabrication system shown in different embodiments.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present invention. It will be apparent to oneskilled in the art, however, that certain embodiments may be practicedwithout some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well-known processesand elements have not been described in order to avoid unnecessarilyobscuring the present invention. Accordingly, the above descriptionshould not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Eachsmaller range between any stated value or intervening value in a statedrange and any other stated or intervening value in that stated range isencompassed. The upper and lower limits of those smaller ranges mayindependently be included or excluded in the range, and each range whereeither, neither, or both limits are included in the smaller ranges isalso encompassed within the invention, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either or both of those includedlimits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “an aperture” includes aplurality of such apertures, and reference to “the plate” includesreference to one or more plates and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or steps, but they do not preclude thepresence or addition of one or more other features, integers,components, steps, acts, or groups.

What is claimed is:
 1. A method of etching a patterned substrate in asubstrate processing region of a substrate processing chamber, whereinthe patterned substrate includes an exposed titanium nitride region anda region comprising an exposed second material, the method comprising:flowing a fluorine-containing precursor into a remote plasma regionfluidly coupled with the substrate processing region while forming aplasma in the remote plasma region to produce plasma effluents, whereinthe substrate processing region is at least partially separated from theremote plasma region by a showerhead or chamber wall; flowing at leastone additional precursor into the substrate processing region; andetching the exposed titanium nitride region with the precursorcombination including the plasma effluents, wherein the titanium nitrideis etched at a faster rate than the exposed second material, and whereinthe exposed second material comprises at least one of silicon oxide,silicon nitride, and tungsten.
 2. The method of claim 1, wherein the atleast one additional precursor is selected from the group consisting ofhelium, argon, and molecular hydrogen (H₂).
 3. The method of claim 1,wherein the fluorine-containing precursor comprises a precursor selectedfrom the group consisting of atomic fluorine, diatomic fluorine,nitrogen trifluoride, carbon tetrafluoride, hydrogen fluoride, and xenondifluoride.
 4. The method of claim 1, wherein the plasma in the remoteplasma region is a capacitively-coupled plasma.
 5. The method of claim1, wherein the substrate processing region is plasma-free during theetching process.
 6. The method of claim 1, wherein the at least oneadditional precursor consists of either or both of helium and argon. 7.The method of claim 6, wherein the precursor combination includingplasma effluents is substantially devoid of hydrogen.
 8. The method ofclaim 6, wherein the exposed second material comprises silicon oxide andthe selectivity of the etching operation (exposed titanium nitrideregion: exposed silicon oxide region) is greater than or about 5:1. 9.The method of claim 8, wherein the selectivity of the etching operation(exposed titanium nitride region: exposed silicon oxide region) isgreater than or about 10:1.
 10. The method of claim 6, wherein thesubstrate temperature is maintained at or below about 50° C. during theetch process.
 11. The method of claim 10, wherein the substratetemperature is maintained at or below about 10° C. during the etchprocess.
 12. The method of claim 1, wherein the at least one additionalprecursor comprises hydrogen.
 13. The method of claim 12, wherein theexposed second material comprises tungsten and the selectivity of theetching operation (exposed titanium nitride region: exposed tungstenregion) is greater than or about 50:1.
 14. The method of claim 13,wherein the selectivity of the etching operation (exposed titaniumnitride region: exposed tungsten region) is greater than or about 100:1.15. The method of claim 13, wherein the patterned substrate furthercomprises an exposed silicon nitride region and the selectivity of theetching operation (exposed titanium nitride region: exposed siliconnitride region) is greater than or about 10:1.
 16. The method of claim13, wherein the patterned substrate further comprises an exposed siliconoxide region and the selectivity of the etching operation (exposedtitanium nitride region: exposed silicon oxide region) is greater thanor about 5:1.
 17. The method of claim 13, wherein the patternedsubstrate further comprises an exposed tantalum nitride region and theselectivity of the etching operation (exposed titanium nitride region:exposed tantalum nitride region) is greater than or about 10:1.
 18. Themethod of claim 12, wherein the substrate temperature is maintained ator above about 50° C. during the etch process.
 19. The method of claim18, wherein the substrate temperature is maintained at or above about200° C. during the etch process.
 20. The method of claim 12, wherein thehydrogen is flowed into the substrate processing region without beingfirst excited in a remote plasma.
 21. The method of claim 12, whereinthe hydrogen comprises molecular hydrogen (H₂).